TWI499826B - Liquid crystal display with touch screen function and method for detecting external illuminance using the same - Google Patents

Description

Liquid crystal display with touch screen function and method for detecting external illumination

The present invention relates to a liquid crystal display (LCD) having a touch screen function, and more particularly to a technique for embedding a touch screen in an LCD without a separate touch screen device.

An LCD with a touch screen function receives input from a finger or stylus on its surface without a separate input unit, such as a keypad. According to the data detection method, the LCD with the touch screen is divided into a resistive type, a capacitive type, a surface acoustic wave (SAW) type, and an infrared type. However, in each type, since a touch screen panel is attached to the LCD, the thickness of the product is increased, the cost is increased, the yield is lowered, and the angle of view is reduced.

In order to solve these problems, a technique of forming a touch panel in an in-cell type LCD has been developed, such as Korean Patent Application No. 2006-34878, No. 2006-15480, and the like. U.S. Patent Nos. 4,345,248, 5,485,177, 6,995,743, and the like, the disclosure of the disclosure of the disclosure of the disclosure of the disclosure of the disclosure of the disclosure of the disclosure of the disclosure of the disclosure of the disclosure of the disclosure of the disclosure of the disclosure of the disclosure of the disclosure of the disclosure of the disclosure of

For example, in U.S. Patent No. 5,485,177, an array substrate comprises a display area 100 and a photosensitive area 110, as shown in FIG. Referring to FIG. 1, a photosensitive element 113, a switching element 111, and a charge storage element 112 are formed in the photosensitive region 110. One end of the photosensitive element 113 is connected to the charge storage element 112, and the other end is connected to the scan line 115. When a voltage is applied to the scan line 115 connected to the switching element 111, the charge storage element 112 is charged to the voltage applied via the column line 116 of the switching element 111. Each of the photosensitive elements 113 is operative to discharge the charge stored in the charge storage element 112 in response to illumination.

However, a disadvantage of this method of operation is that the load on the scan line is heavy because the charge storage element 112 is connected to each scan line 115. When the resolution of the LCD is increased, it is not necessary to have a photosensitive area for each pixel. In this case, a load difference occurs between the scanning line of the pixel having the photosensitive area and the scanning line of the pixel having no photosensitive area, thereby reducing the pixel quality of the LCD.

In another example, U.S. Patent No. 6,995,743 is directed to an LCD wherein an array substrate comprises a display area and a photosensitive area. Fig. 2 is a circuit diagram of a conventional LCD having a touch screen function, and Fig. 3 is a cross-sectional view of the LCD.

Referring to FIG. 2, the photosensitive region 120 of the array substrate includes a photosensitive element 122, a switching element 123, and a charge storage element 121. In general, a photonic crystal is used as the photosensitive element 122. The gate and source terminals of the optoelectronic crystal are connected to a common line 125. The drain terminal of the optoelectronic crystal is connected to one end of the switching element 123 and the charge storage element 121. The other end of the charge storage element 121 will be connected to the common line 125. As a result, the gate and source terminals of the phototransistor 122 are electrically connected. The gate terminal of switching element 123 will be connected to scan line 126. Other terminals of switching element 123 will be connected to a readout system 127. Referring to FIG. 3, the upper portion of the switching element 123 is covered by a black matrix 128 for compartmentalizing external light; and the upper portion of the optoelectronic crystal 122 is open and exposed to external light as indicated by symbol 129.

When light is incident on the photosensor 122, current will flow through the optoelectronic crystal 122, and the output based on the illumination difference incident on the optoelectronic crystal 122 will be read out via the switching element 123.

Here, the maximum read voltage is proportional to the difference between the gate-source voltage of the photo transistor 122 and the voltage stored in the charge storage element 121 via the switching element 123. The voltage stored in the charge storage element 121 via the switching element 123 is set by the readout system 127, and the gate-source voltage of the optoelectronic crystal 122 is supplied to the common voltage of the common line 125 of the LCD. This common voltage will have different values depending on the LCD operating technique. For example, in the dot inversion technique, when the LCD data voltage ranges from 0 to 10 V, the common voltage value is calculated by subtracting the offset voltage from the intermediate data voltage. When the LCD data voltage range is -5 to 5V, the common voltage value is calculated by subtracting the offset voltage from 0V corresponding to the intermediate value. In the online inversion technique, when the LCD data voltage range is 0 to 5 V, the common voltage value is calculated by subtracting the offset voltage from 0 to 5 V which changes the polarity.

As a result, in a conventional LCD having a touch screen function, the difference between the voltages applied across the charge storage element becomes a difference between the common voltage and the voltage applied by the readout system. Therefore, the problem is that when the difference between the voltages applied across the charge storage element is small, the maximum read voltage is lowered.

The present invention relates to a liquid crystal display (LCD) having a touch screen function and a method for detecting external illumination thereof, which is capable of connecting a charge storage element to a display operation in a photosensitive region of an array substrate The common line reduces the load on the scan line and can increase the maximum read voltage by increasing the voltage applied to both terminals of the charge storage element.

According to an aspect of the present invention, an LCD having a touch screen function includes: an array substrate having a display area and a photosensitive area divided by a data line, a scan line, and a common line, wherein The photosensitive region includes: a switching element having a first terminal connected to the (n-1)th scan line for receiving the selection signal and a second terminal connected to the readout system; a charge storage element a first terminal connected to the third terminal of the switching element and a second terminal connected to the common lines; and a photosensitive element having a first connection to the nth scanning line a terminal and a second terminal connected to the first terminal of the charge storage element, wherein when the photosensitive element is activated according to external illumination, the charge storage element is discharged and the readout system detects external illumination The difference.

When the (n-1)th scanning line is selected, the switching element may be activated and the charge storage element may be charged to the reference voltage of the readout system, and when the nth scanning line is selected, the photosensitive element May be activated and the charge storage element may be charged to the selection voltage of the nth scan line, and when the (n-1)th scan line is reselected, the readout system may measure the charge storage The amount of charge on the component to detect differences in external illumination.

When the (n-1)th scanning line is selected, the switching element may be activated and the charge storage element may be charged to the reference voltage of the readout system, and when the nth scanning line is selected, the photosensitive element May be activated and the charge storage element may be charged to the selection voltage of the nth scan line, and when the (n-1)th scan line is reselected, the readout system may measure the charge storage The amount of discharge of the component to detect differences in external illumination.

When the (n-1)th scan line is selected, the switching element may be activated and the charge storage element may be charged to the reference voltage of the readout system, and when the nth scan line is selected, the light sensitive The component may be activated and the charge storage component may be charged to the selected voltage of the nth scan line. When the (n-1)th scan line is reselected, if the voltage stored in the charge storage element is lower than the reference voltage of the readout system, the readout system can measure from the readout system to the The amount of charge of the charge storage element is used to detect a difference in external illumination, and if the voltage stored in the charge storage element is higher than the reference voltage of the readout system, the readout system can measure from the charge storage element The amount of discharge of the readout system is used to detect differences in external illumination.

The selection voltage of the scan line may be higher than the reference voltage of the readout system.

The switching element may be a transistor, wherein the first terminal is a gate, the second terminal is a source, and the third terminal is a drain.

The photosensitive element may be a photodiode, wherein the first terminal is an anode and the second terminal is a cathode. The photosensitive element may further comprise a third terminal connected to the scan line and possibly a photovoltaic crystal, wherein the first terminal is a source, the second terminal is a drain, and the third terminal is a gate.

According to another aspect of the present invention, an external illumination difference in a readout system is detected when a photosensitive element is activated according to the external illumination and a charge storage element is discharged in an LCD having a touch screen function. The method, wherein a photosensitive region comprises a switching element, the charge storage element, and the photosensitive element, the method comprising: when the (n-1)th scan line is selected, starting the switching element and the charge storage element Charging to a reference voltage of the readout system; when the nth scan line is selected, the photosensor is activated and the charge storage element is charged to the selected voltage of the nth scan line; and when reselected in the next frame When the (n-1)th scan line is activated and the switching element is activated, if the voltage stored in the charge storage element is higher than the reference voltage of the readout system, by measuring from the charge storage element to the readout The amount of discharge of the system to detect the difference in external illumination, and if the voltage stored in the charge storage element is lower than the reference voltage of the readout system, Readout system to the amount of charge of the charge storage elements to detect the difference in exterior lighting.

The selection voltage of the scan line may be higher than the reference voltage of the readout system.

The switching element of the photosensitive region may include a first terminal connected to a scan line and a second terminal connected to the readout system, the charge storage element may include a third terminal connected to the switching element a first terminal and a second terminal connected to a common line; and the photosensitive element may include a first terminal connected to a scan line and a second terminal connected to the first terminal of the charge storage element terminal.

The switching element may be a transistor, wherein the first terminal is a gate, the second terminal is a source, and the third terminal is a drain.

The photosensitive element may be a photodiode, wherein the first terminal is an anode and the second terminal is a cathode. The photosensitive element may further comprise a third terminal connected to the scan line and possibly a photovoltaic crystal, wherein the first terminal is a source, the second terminal is a drain, and the third terminal is a gate.

Exemplary embodiments of the present invention will be described in detail below with reference to the accompanying drawings. While the invention has been shown and described with reference to the embodiments of the present invention, it will be understood by those skilled in the art that various modifications can be made without departing from the spirit and scope of the invention.

Fig. 4 is a schematic view of an LCD having a touch screen function, and Fig. 5 is a view showing the principle of operation of the first and second substrates of Fig. 4.

The present invention relates to a technique for forming a touch screen panel in a honeycomb-type LCD. In the LCD, an array substrate includes a display area for display operation and a photosensitive area, the photosensitive area being provided with a photosensitive element, a charge storage element, and a switching element.

Referring to Figures 4 and 5, the LCD includes a first substrate 200 and a second substrate 201. The second substrate 201 is formed to face the first substrate 200 in parallel. The second substrate 201 includes: a black matrix layer for covering an area where the pixel electrode is not formed; and a color filter layer for performing image color. In the second substrate 201, a dot-shaped separator is selectively formed to maintain a predetermined distance from the first substrate 200.

The first substrate 200 includes: a plurality of horizontal scanning lines formed to drive the liquid crystal; a plurality of data lines formed to intersect the scanning lines; a switching element 202 formed to be used for the scanning line Data input at the intersection with the data line; and a pixel electrode and a common electrode that are connected to the switching element and that are formed to apply a voltage to the liquid crystal.

In the example shown in Fig. 5, a display area and a photosensitive area whose characteristics change with external illumination are formed on the first substrate 200 in the LCD having the touch screen function. The photosensitive area and the display area comprise switching elements 203 and 202, respectively. It can be seen in the second substrate 201 that a portion corresponding to the display region and a portion where a photosensitive member is placed in the photosensitive region are not covered by the black matrix.

As shown in FIGS. 4 and 5, external light reaches the photosensitive region via an opening in the second substrate 201. When a human finger covers the opening of a special photosensitive area, external light does not pass through the covered portion, and thus, the photosensitive member of the photosensitive area does not operate.

6A and 6B are circuit diagrams of an LCD having a touch screen function according to an exemplary embodiment of the present invention.

Referring to FIGS. 6A and 6B, the LCD with touch screen function has a data line 307, a scan line 309, and a common line 308, thereby dividing a display area and a photosensitive area on an array substrate. Here, a photosensitive region 300 includes a switching element 301, a charge storage element 302, and a photosensitive element 303.

Switching element 301 has a gate terminal connected to scan line 309, a source terminal connected to readout system 305, and a drain terminal connected to charge storage element 302. Switching element 301 transmits the reference voltage supplied from readout system 305 to charge storage element 302. Switching element 301 is controlled by the selection signal of scan line 309. The switching element 301 is configured as a thin film transistor (TFT) and a semiconductor layer of the transistor is made of amorphous germanium (a-Si).

The charge storage element 302 has a first terminal connected to the drain terminal of the switching element 301 and a second terminal connected to the common line 308. The charge storage element 302 receives and stores a reference voltage transmitted from the switching element 301 and a selection voltage transmitted from the scanning line 309 of the photosensitive element 303. A capacitor can be used as the charge storage element 302.

The photosensitive member 303 is a device that allows current to flow when external light is irradiated. A photodiode or a photonic crystal can be used as the photosensitive member 303. Fig. 6A shows an example in which a photodiode is used as the photosensitive member 303, and Fig. 6B shows a photonic crystal as an example of the photosensitive member 303.

Referring to FIG. 6A, when the photosensitive element 303 is a photodiode, the anode terminal is connected to the scan line 309, and the cathode terminal is connected to the first terminal of the charge storage element 302. However, the anode terminal of the photosensitive member is connected to the next nth scanning line in the same photosensitive region, rather than the (n-1)th scanning line connected to the gate terminal of the switching element 301.

Referring to FIG. 6B, when the photosensitive element 303 is a photoelectric crystal, its interconnected gate and source terminals are connected to the scan line 309, specifically, the next nth scan line in the same photosensitive region, Rather than the (n-1)th scan line connected to the gate terminal of the switching element 301. The drain terminal of the photosensitive element 303 is connected to the first terminal of the charge storage element 302, and the selection voltage of the scan line 309 is supplied to the charge storage element 302.

Fig. 7 is a graph showing the relationship of optical current as a function of external light in the photosensitive member. As the illumination of the external light increases, the optical current through the photosensitive element increases, as shown in Figure 7.

Next, the operation of the circuits in the circuits shown in Figs. 6A and 6B will be explained with reference to Fig. 8.

First, when the (n-1)th scan line 309 of FIGS. 6A and 6B is selected, the switching element 301 is activated, and thus the reference voltage of the readout system 305 connected to the source terminal of the switching element 301 is Is applied to node A. That is, the charge storage element 302 will be charged to the reference voltage of the readout system 305. In the example shown in Fig. 8, the reference voltage of the readout system is 3V, and the selection voltage of the scan line is about 15V. At this time, it can be seen that the voltage of the node A is lower than the reference voltage due to the relationship of parasitic capacitance or the like.

Next, when the nth scanning line is selected, the photosensitive element 303 is activated, and thus, the selection voltage of the scanning line 309 is applied to the node A. Referring to Fig. 8, it can be seen that node A of charge storage element 302 is charged to about 13 volts, which is higher than the reference voltage of the readout system when the nth scan line is selected. That is, it can be seen that the voltage applied to the two terminals of the charge storage element by convention is as low as the reference voltage; however, as shown in Fig. 8, an exemplary embodiment of the present invention is applied to the charge storage. The voltage at both terminals of the component is as high as the selected voltage of the scan line.

When external light is incident on the photosensitive region in the LCD having the photosensitive region, current flows through the photosensitive member 303. When the photosensitive element 303 is activated according to external illumination, the charge stored in the charge storage element 302 may leak leakage current to the scan line 309. That is, the charge storage element 302 is discharged due to the amount of leakage current according to external illumination applied to the photosensitive element 303 before the next (n-1)th scanning line is selected.

Next, when the (n-1)th scan line 309 is reselected, the charge storage element 302 is recharged to the reference voltage via the switching element 301. The readout system 305 detects the difference in external illumination by measuring the amount of charge. When the amount of discharge is small and the voltage of the node A of the charge storage element 302 is higher than the reference voltage, the difference in external illumination can be detected by measuring the amount of discharge from the node A to the readout system 305. Depending on the difference in external illumination, it is possible to distinguish between the part touched by the finger and the part that is not touched.

As described above, according to the present invention, a charge storage element is connected to a common line for display operation in a photosensitive area, thereby reducing the load of the scanning line and reducing the line delay when a scanning line is selected.

In a conventional manner, the voltage applied to both terminals of the charge storage element is as low as the reference voltage. However, since the voltages of the two terminals of the charge storage element applied to the photosensitive region are as high as the selection voltage of the scanning line, the present invention can increase the maximum read voltage.

It will be apparent to those skilled in the art that various modifications may be made to the above-described exemplary embodiments of the present invention without departing from the spirit or scope of the invention. Accordingly, the invention is intended to cover all modifications that come within the scope of the appended claims.

100. . . Display area

110. . . Photosensitive area

111. . . Switching element

112. . . Charge storage element

113. . . Photosensitive element

115. . . Scanning line

116. . . Line

120. . . Photosensitive area

121. . . Charge storage element

122. . . Photosensitive element

123. . . Switching element

125. . . Common line

126. . . Scanning line

127. . . Readout system

128. . . Black matrix

129. . . External light

200. . . First substrate

201. . . Second substrate

202. . . Switching element

203. . . Switching element

300. . . Photosensitive area

301. . . Switching element

302. . . Charge storage element

303. . . Photosensitive element

305. . . Readout system

307. . . Data line

308. . . Common line

309. . . Scanning line

A. . . node

FIG. 1 is an example of a circuit diagram of a conventional LCD having a touch screen function of one of a display area and a photosensitive area.

Figure 2 is a circuit diagram of a conventional LCD with a touch screen function.

Figure 3 is a cross-sectional view of a conventional LCD having a touch screen function.

Figure 4 is a schematic diagram of a honeycomb internal LCD with touch screen function.

Fig. 5 is a detailed view showing the principle of operation of the first and second substrates shown in Fig. 4.

6A and 6B are circuit diagrams of a honeycomb internal type LCD having a touch screen function according to an exemplary embodiment of the present invention.

Fig. 7 is a graph showing the relationship of optical current as a function of external light in the photosensitive member shown in Figs. 6A and 6B.

Fig. 8 is a schematic view showing the operation of the circuit in the circuit diagrams shown in Figs. 6A and 6B.

200. . . First substrate

201. . . Second substrate

Claims (16)

A liquid crystal display (LCD) having a touch screen function includes: an array substrate having a display area and a photosensitive area divided by a data line, a scan line, and a common line, wherein the photosensitive area includes: a switching element having a first terminal connected to the (n-1)th scanning line of the scan lines for receiving a selection signal and a second terminal connected to the readout system; a charge storage element a first terminal connected to the third terminal of the switching element and a second terminal connected to the common line; and a photosensitive element having a first connected to the scan line a first terminal of the scan line and a second terminal connected to the first terminal of the charge storage element, wherein the charge storage element is discharged when the photosensitive element is activated according to external illumination and the readout system Will detect the difference in external lighting. The liquid crystal display of claim 1, wherein when the (n-1)th scanning line is selected, the switching element is activated and the charge storage element is charged to a reference voltage of the reading system. When the nth scan line is selected, the photosensitive element is activated and the charge storage element is charged to the selection voltage of the nth scan line, and when the (n-1)th scan line is reselected, The readout system detects the difference in external illumination by measuring the amount of charge of the charge storage element. The liquid crystal display of claim 1, wherein when the (n-1)th scanning line is selected, the switching element is activated and the charge storage element is charged to a reference voltage of the reading system. When the nth scan line is selected, the photosensitive element is activated and the charge storage element is charged to the selection voltage of the nth scan line, and when the (n-1)th scan line is reselected, The readout system detects the difference in external illumination by measuring the amount of discharge of the charge storage element. The liquid crystal display of claim 1, wherein when the (n-1)th scanning line is selected, the switching element is activated and the charge storage element is charged to a reference voltage of the reading system. And when the nth scan line is selected, the photosensitive element is activated and the charge storage element is charged to the selected voltage of the nth scan line, and wherein, when the (n-1)th scan is reselected In the case of a line, if the voltage stored in the charge storage element is lower than the reference voltage of the readout system, the readout system can detect external illumination by measuring the amount of charge from the readout system to the charge storage element. a difference, and if the voltage stored in the charge storage element is higher than the reference voltage of the readout system, the readout system can detect the external by measuring the amount of discharge from the charge storage element to the readout system The difference in lighting. The liquid crystal display of claim 2, wherein the selection voltage of the scan line is higher than a reference voltage of the readout system. The liquid crystal display of claim 3, wherein the selection voltage of the scan line is higher than a reference voltage of the readout system. The liquid crystal display of claim 4, wherein the selection voltage of the scan line is higher than a reference voltage of the readout system. The liquid crystal display according to claim 1, wherein the switching element is a transistor, wherein the first terminal is a gate, the second terminal is a source, and the third terminal is a drain. The liquid crystal display of claim 1, wherein the photosensitive element is a photodiode, wherein the first terminal is an anode and the second terminal is a cathode. The liquid crystal display of claim 1, wherein the photosensitive element further comprises a third terminal connected to the scan line and is a photoelectric crystal, wherein the first terminal is a source and the second terminal is a The pole is the third terminal. A method for detecting a difference in external illumination in a readout system when a photosensitive element is activated according to external illumination and a charge storage element is discharged in a liquid crystal display having a touch screen function, wherein a photosensitive region includes a a switching element, the charge storage element, and the photosensitive element, the method comprising: when selecting the (n-1)th scan line in the scan line, activating the switching element and charging the charge storage element to the readout system Reference voltage; when the nth scan line in the scan line is selected, the photosensor is activated and the charge storage element is charged to the selected voltage of the nth scan line in the scan lines; and when in the next frame Reselecting the (n-1)th scan line in the scan line and when the switching element is activated, if the voltage stored in the charge storage element is higher than the reference voltage of the readout system, the charge is stored from the charge The amount of discharge from the component to the readout system to detect a difference in external illumination, provided that the voltage stored in the charge storage component is lower than the readout system The reference voltage, then, by measuring the amount of the read-out system to charge the charge storage element to detect the difference in exterior lighting. The method of claim 11, wherein the selection voltage of the scan line is higher than a reference voltage of the readout system. The method of claim 11, wherein the switching element of the photosensitive region comprises a first terminal connected to the scan line and a second terminal connected to the readout system, the charge storage element A first terminal connected to the third terminal of the switching element and a second terminal connected to a common line; and the photosensitive element includes a first terminal connected to the scan line and a connected to a second terminal of the first terminal of the charge storage element. The method of claim 13, wherein the switching element is a transistor, wherein the first terminal is a gate, the second terminal is a source, and the third terminal is a drain. The method of claim 13, wherein the photosensitive element is a photodiode, wherein the first terminal is an anode and the second terminal is a cathode. The method of claim 13, wherein the photosensitive element further comprises a third terminal connected to the scan line and is a photoelectric crystal, wherein the first terminal is a source and the second terminal is a The pole is the third terminal.